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Technology: From tungsten to LED

Technology: From tungsten to LED
The Source Four LED Series is an alternative to the tungsten ellipsoidal

Technology: From tungsten to LED

With tungsten fixtures on the way out in several territories, how well can LEDs do the job? We asked ETC’s Rory Fraser-Mackenzie

The question of how faithfully modern LED lighting fixtures can replicate the output of traditional tungsten bulbs is not a new one. But in light (pardon the pun) of the emergence of legislation in several territories to ban tungsten – most notably by the European Union (EU) – and the transition to more energy-efficient LED bulbs, the debate is timelier than ever. Furthermore, big advances have been made by manufacturers in recent years in regard to the quality of light from LED fixtures.

Stage lighting products are not exempt from the tungsten ban in the EU, and they’re usually not upgradable with a simple bulb change. This leaves some houses of worship in a predicament. Regardless of whether your ministry wants to replace these fixtures or not, or whether you’re based in a territory phasing out tungsten, if changes or replacements need to be made, it’s a sensible choice to transition (slowly) to an all-LED lighting rig.

One company that’s focused its attention heavily on this topic is ETC, so we asked European market manager, Rory Fraser-Mackenzie, about ETC’s current thoughts on this topic.

Rory Fraser-Mackenzie
Rory Fraser-Mackenzie

Should LED fixtures replicate the output of traditional lamps?

Lighting designers and end-users want lights to behave in a way that they are familiar with, particularly in regard to fade performance, colour rendering and brightness. Not all sites switch to a full LED system at once, which means that LEDs will often be operating alongside tungsten fittings. So it’s important they work similarly and to ensure any new LED fixtures you are adding to your installation have the right features to work well with tungsten so they look similar. Adding some 5,600K daylight fittings into a room predominantly lit with tungsten might not give you the intended effect.

What tungsten attributes are ETC trying to replicate?

ETC works hard on the spectral makeup of the light output so that the objects being lit look ‘right’ by paying particular attention to how skin tones are rendered and also how architectural finishes and fabrics appear. Additionally, as a tungsten lamp is dimmed to a low level, its colour temperature changes and it gives off a warmer glow. ETC includes technologies in our products that can mimic this change; we call this feature ‘Red Shift’ or ‘Fade to Warm’ and it’s particularly important in white light sources and in environments where lighting is faded out slowly, or set at low intensities.

Our work in the theatre and entertainment markets also requires us to produce luminaires that dim beautifully without flickering, stepping or snap changes in level, and we use this experience in the development of all our luminaires.

In addition, our fixtures are designed to have similar form factors to traditional tungsten luminaires; they can use the same optical systems – lenses, etc. – as our tungsten fittings, and in similar-sized fixture bodies so they can be installed in the same locations as traditional luminaires to make the switch to LED easier.

Desire series wash lights – a series of LED wash lights integrating ‘Red Shift’ technology to replicate the colour temperature change of dimming incandescent bulbs
Desire series wash lights – a series of LED wash lights integrating ‘Red Shift’ technology to replicate the colour temperature change of dimming incandescent bulbs

Which attribute is the most difficult to replicate?

The quality of the light output is still the biggest challenge. This used to be measured using CRI with tungsten bulbs, but the industry has now shifted to using TM-30 (IES TM-30-15) to assess the LED light quality on skin tones and the objects being lit. Good dimming is also still hard for manufacturers of LED luminaires, but our work for the theatre industry means we have lots of experience.

Are conventional fixtures still superior to LED in any area?

When very bright white light is needed, or very high rendering quality, the best option is still an incandescent fixture for the time being.

In what ways is LED superior to traditional lamps?

Additive colour mixing of LEDs not only gives much higher efficacy (lumens per watt) but also finer control of the output. LED luminaires allow you to tune the output as needed, adjusting the colour temperature or quality of light without changing the source. There is a lot of research happening at the moment focused on ‘Human Centric’ lighting that indicates that there may be medical benefits from adjusting the colour temperature of the lighting around us at different times of day. Having tunable luminaires then becomes a desirable proposition beyond just aesthetics. LED fixtures also boast a much longer life span (25,000–50,000 hours) and their increase in efficiency means less heat is produced, which can reduce the need for HVAC, saving further energy costs.

Source 4WRD – an LED retrofit module to replace the tungsten lamp in a traditional Source Four ellipsoidal
Source 4WRD – an LED retrofit module to replace the tungsten lamp in a traditional Source Four ellipsoidal

Colour matching aside, what are the drawbacks of mixing bulb types?

Some LED fixtures don’t fade well, or their fade performance is very different to how a traditional tungsten fitting dims, either by having a different curve – i.e. the brightness falls off at a different rate, often with snap changes in levels or flickering at some intensities – or not changing colour temperature at low intensities. LED fixtures may also require different power or control infrastructure to conventional lamps, so having a mix may be more complicated than just matching the light output. ETC’s ThruPower products (which can be both traditional dimmer and switched power at the flick of a switch) were designed with this in mind, allowing installations to move to LED over a period of time.

Can LED fixtures one day replace tungsten lamps completely?

Yes, probably. It’s almost happened already and regulatory changes like the EU’s Ecodesign regulations are only accelerating the change. There is also still room for improvement with LED fixtures. Advances in thermal management will allow for smaller, brighter fixtures, and the reduction in heat will remove the need for fans, making them quieter. OLED technology will allow for more complicated shapes of light source, allowing for complex curves and large, diffuse, flexible panels. There has been a lot of scientific research into OLEDs over the past few decades and it’s already making its way into commercial products, particularly in situations where no other light source will fit. It’s definitely a technology to look out for.

This article was first published in the May-June 2019 edition of Worship AVL. Subscribe at www.proavl-central.com/subscribe/worship




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